The aforementioned Provisional Application No. 60/194,806 and U.S. application Ser. No. 09/733,351 are hereby incorporated by reference in their entirety.
The present invention relates to a disc drive microactuator, and more particularly to a high resolution positioning mechanism implemented at the transducer level for selectively moving a transducer portion of the slider radially with respect to circumferential data tracks of a rotatable disc.
The density of concentric data tracks on magnetic discs continues to increase (that is, the size of data tracks and radial spacing between data tracks are decreasing), requiring more precise radial positioning of the head. Conventionally, head positioning is accomplished by operating an actuator arm with a large-scale actuation motor, such as a voice coil motor, to radially position a head on a flexure at the end of the actuator arm. The large-scale motor lacks sufficient resolution to effectively accommodate high track-density discs. Thus, a high resolution head positioning mechanism, or microactuator, is necessary to accommodate the more densely spaced tracks.
Another challenge as the track density of magnetic discs increases is that the flying height of the transducing head above the surface of the disc must decrease for effective data writing and reading, without compromising the reliability of the head-to-disc interface due to wear. As the flying height becomes lower, it becomes more critical to maintain the flying height precisely at a desired value, since a slight decrease may cause contact between the head and the disc which could cause a catastrophic failure, and a slight increase during writing or reading could cause errors in the transducing of data with the disc.
One promising approach for high resolution head positioning involves employing a high resolution microactuator in addition to the conventional lower resolution actuator motor, thereby effecting head positioning through dual-stage actuation. Various microactuator designs have been considered to accomplish high resolution head positioning. Some designs are employed to deform disc drive components such as the actuator arm or the flexure in order to achieve minute displacements by bending. Other designs introduce a separate microactuator component at an interface between disc drive components. While many previous microactuator designs are able to deliver satisfactory micropositioning performance, their effectiveness is inherently limited by the sheer mass that the microactuators are designed to move. In order to move or bend one or more of the disc drive components, the microactuator employed must provide a relatively large amount of force, which requires either a complex or relatively massive microactuator motor mechanism.
A number of configurations have also been proposed to adjust the flying height of the head above the surface of the disc. Several of these proposed configurations employ an active deforming element such as a piezoelectric element to deform the slider itself, referred to in the art as xe2x80x9ccrown control.xe2x80x9d With cost being a prime consideration in the commercial viability of a disc drive, the economic feasibility of adding both a crown control microactuator and a head positioning microactuator is questionable. Crown control microactuators also have a frequency response that is limited by the time it takes for the air bearing pressure between the head-carrying slider and the disc to adjust to a new slider profile. This adjustment time is roughly equal to the length of the slider divided by the surface velocity of the disc, which is typically on the order of several tenths of a millisecond. Between the cost and frequency response concerns, the combination of a crown control microactuator and a head positioning microactuator does not represent an ideal solution for a high track density disc drive.
A microactuator designed to move only a transducer-carrying portion of the slider with respect to the main portion of the slider is disclosed in U.S. application Ser. No. 09/007,007 which is assigned to Seagate Technology, Inc., the same assignee as the present invention. The present invention provides another microactuator for moving a transducer-carrying portion of the slider with high resolution and frequency response, while also providing flying height adjustment capability in the same microactuator configuration. The microactuator of the present invention is readily and inexpensively manufacturable for economic feasibility.
The present invention is a slider for carrying and finely adjusting both a radial position and a flying height of a transducing head with respect to a track of a rotatable disc. The slider includes a stator portion carried by a support structure such as a flexure of a disc drive system. A plurality of springs extend from the stator portion and are flexible in a lateral direction (for radial positioning) and in a vertical direction (for flying height control). A rotor portion is connected to the stator portion by the plurality of springs. The rotor portion carries the transducing head. The stator portion includes a plurality of stator electrodes, and the rotor portion includes a plurality of rotor electrodes suspended between the stator electrodes. Selected voltages are applied to the stator electrodes and the rotor electrodes to create a selected force in the lateral and vertical directions for moving the rotor portion with respect to the stator portion to finely adjust the radial position and flying height of the transducing head.